Magnetic frequency divider



y 1952 H. J. M CREARY 2,602,153

MAGNETIC FREQUENCY DIVIDER Filed June 21, 1950 2 SHEETS-SHEET1 20 cm Q AH INPUT #Y in I30 V 60C OUTPUT 20 cm INPUT 130 v so cm no I D 0.. D O 2 6' MlLLl-AMPERES OUTPUT IN VEN TOR. HAROLD J. M CREARY AIIORNEY July 1, 1952 H. J. MCCREARY 2,602,153

MAGNETIC FREQUENCY DIVIDER Filed June 21, 1950 2 SHEETS-SHEET 2 FIG. 4

OUTPUT INPUT I30 v so CY 29 FIG. 5

OUTPUT 2o CY.

INPUT 130 v so cx OUTPUT INPUT \30 v 60 CY INVENTOR.

HAROLD J. M CREARY ATTORNEY Patented July 1, 1952 UNITED STATES -TENT OFFICE MAGNETIC FREQUENCY DIVIDER Application June 21, 1950, Serial No. 169,489

This invention relates in general to frequency changers, and more particularly to a means for deriving current of one frequency from a source of current of a .difierent frequency.

An object of the present invention is to provide a sub-frequency generator of the magnetic cross valve type having an improved load regulationcharacteristic by controlling the direct current magnetization at the center of the cross valve-core.

Another object of the present invention is to provide a-sub-frequency generator of the magnetic cross valve type having self-starting characteristics by providing .a continuous pulsating magnetizing current.

-A feature of the present invention is the use of a cross-coil on a generator of the cross valve type having a continuous pulsating current flowing therein.

Another feature of the present invention is the use of an electrolytic condenser as a D. C. input feed to the cross winding to improve the selfstarti-ng and load regulation characteristics.

Other objects of the invention will-appear upon a further perusal .of the specification taken in conjunction with the accompanying drawings which illustrate several of the embodiments of the invention in the form of schematiqdiagrams.

Fig. 1 is a diagrammatic representation of a magnetic cross valve sub-frequency generator utilizing a direct current so as to excite aresonant circuit to provide a continuousppulsating current in the cross winding.

Fig, .2 is .a diagrammatic representation of a magnetic cross valve sub-frequency generator having a winding coupled to the input winding and the current flowing therefrom rectified to provide a continuous pulsatingcurrent for the cross winding.

Fig. ;3 is a graphical illustration of the load regulation for Fig. 2.

Fig. 4 is a diagrammatic representation of a magnetic cross valve sub-frequency generator using permanent magnets to provide a biasing flux at the center of the magnetic cross valve core.

Fig. 5 shows a diagrammatic representation of a magnetic cross valve sub-frequency generator in which the leg coils produce a biasing flux by rectifying the input signal.

Fig. 6 is a diagrammatic representation of a magnetic cross valve sub-frequency generator having a biasing flux produced .by using low voltage rectifiers on the leg coils.

In the magnetic cross valve systems of the type 11 Claims. (Cl. 32168) herein used two windings are displaced by 90 degrees so as to provide that the mutual inductance between the respective windings is substantially Zero at partial saturation, but which induces odd harmonics in the secondary winding .at high degrees of saturation.

In the present invention cross coils are energized by continuous pulsating current which provides a D. C. flux to bias the cross valve core to a point close to saturation and thereby provides a self-starting system. The frequency of the cross coil added to the frequency of the secondary winding will equal the input signal. The oscillating frequency of the cross coil is caused by a flux diiierential between the D. C. saturating flux and the flux produced by the input signal. The oscillating frequency for the output winding is provided by the saturating flux and the flux produced by the oscillation of the cross coil. In some instances a permanent magnet is used to provide the saturating flux and the cross coil will provide an alternating current to produce an alternating flux which is superimposed on the D. C. flux produced by the permanent magnets.

Referring now to Fig. l, the cross valve 5 herein used may be of the type shown in Patent No. 2,455,078, issued on November 30, 1948, to the present inventor, Patent No. 2,461,992, issued on February 15, 1949, to the present inventor and Patent No. 2,445,857, issued on July 27, 1948, to the present inventor. The cross valve-5 has two intersecting members. A primary coil 1 is wound through a pair of diagonal corners of the intersection. Serially connected to the primary wind ing 1 are two auxiliary windings 9 and 8. An input signal which may be 130 volts cycles is used to energize the primary winding 1 and the auxiliary windings 8 and 9. The auxiliary windings 8 and 9 are wound around the two different intersecting members of the crossvalve 5. A cross winding 6 is wound through the other diagonal corners of the intersection so as to be displaced degrees from the primary winding. A battery I is used to energize the resonating circuit of the cross winding 6. prises inductance coil 2, condenser 3 and cross winding 6. A secondary winding from which the output signal is produced comprises two serially connected coils I0 and II. Coil in is wound around one of the intersecting members of the cross valve 5 and the coil I I is wound around the other intersecting member of the cross valve 5. The output is taken from thesecondary winding across the condenser I2. The oscillating circuit for the secondary winding comprises condenser The resonating circuit com- I2 and coils I and II. In more detail, a 60 cycle input signal energizes the auxiliary windings 9 and 8 and the primary winding 1. Concurrently, the battery I energizes the resonant circuit comprising inductance choke 2, condenser 3, and the cross winding 6. As a result thereof a continuous pulsating flux is produced through the intersecting legs of the cross valve by the current flow through the cross winding 6. A D. C. saturating flux is thereby produced. In response to the cross valve core 5 reaching the point of saturation which is produced by the D. C. biasing flux, the secondary circuit comprising the windings l0 and II and condenser I2 will oscillate at the desired frequency. The secondary circuit is tuned to the desired sub-frequency which in this instance is cycles. The current flow in the coils I0 and II is produced by a flux differential of the pulsating fiux produced by the cross winding 6. The current flow in the cross winding 6 is an alternating current superimposed on a direct current. The output frequency plus the alternating frequency of the cross winding is equal to the input frequency.

Referring now to Fig. 2 an input signal source is provided to energize the primary winding I1 and the auxiliary windings I8 and I9. The cross valve [3 herein used may again be of the type disclosed in the previously mentioned patents to the present inventor. The cross valve herein used has two intersecting members. A primary coil I! is wound through two opposite diagonal corners iii of the intersection and is serially connected to two auxiliary windings I8 and I9. The auxiliary winding I8 is wound around one intersecting member, While the other auxiliary coil I9 is wound around the other intersecting member. A power supply providing 130 volts at 60 cycles is used to energize the windings ll, I8 andl9. A cross winding 20 is wound around the other diagonal corners of the intersection so as to be displaced 90 degress from the primary winding I I. An additional winding 10 is wound through the same diagonal corners of the intersection as is wound the primary winding I! and is inductively coupled to the primary winding. The additional winding 10 is connected to a pair of opposite junctions of the bridge rectifier comprising rectifiers 24, 25, 26 and 21. At the opposite junctions from which the additional winding 18 is connected, a 500 mf. electrolytic condenser 23 is connected to the bridge rectifier. In parallel with the electrolytic condenser 23 is connected an oscillating circuit comprising inductance coil 22, condenser 2I and cross coil 20. secondary windings I5 and I6 and the condenser I4. The secondary winding I5 is wound around one leg of the cross valve I3 at a point opposite that from which the auxiliary winding I8 is wound. The other secondary winding I6 is wound around the other intersecting member of the cross valve I3 at a point opposite that from which the auxiliary winding I9 is wound. The secondary windings I5 and I6 and the condenser I4 are tuned to the desired output frequency, which in this instance is 20 cycles. The auxiliary windings I8 and I9 may have seventy-five turns each whereas the primary winding I! may have one hundred-fifty. The additional winding 10 may have fourteen turns and the cross winding 20 may have five hundred turns. The condenser 2I may be a 30 mf. condenser. The secondary windings I6 and I5 may each have five hundred turns. Condenser I4 may be a 12 mi. condenser. The output frequency under the present conditions The output circuit comprises the will be a 20 cycle signal at volts. In more detail, the power supply energizes the auxiliary windings I8 and I9 and the serially connected primary winding [1 and thereupon the additional winding I0 is energized by magentic coupling between the primary winding I1 and the additional winding Ill. The frequency of the induced current in additional Winding I0 is 60 cycles which is the same frequency as the primary winding. The current flow in the additional winding 'lfl provides a D. C. current feed to the cross coil 20 over the following paths: additional winding 70, rectifier 26, choke 22, cross winding 29, rectifier 24 and the other end of additional winding 10. The other path for the alternating current flow is as follows: additional winding I0, rectifier 21, choke 22, cross winding 20, rectifier 25 and the other end of additional winding 18'. Current flow for the additional winding 79 is rectified to charge the condenser 23 in the following manner: additional winding 10, rectifier 2 I5, condenser 2 3, rectifier 24 to the other end of the additional winding I0 and the return path for the alternating current for additional winding 10 is as follows: additional winding ID, rectifier 21, condenser 23, rectifier 25 and back to the additional winding 10. The D. C. voltage produced in condenser 23 is used to aid the load regulation characteristics. The inductance coil 22 is used for damping the ripples produced in the rectifying process. The circuit including condenser H and cross winding 20 is tuned to oscillate at 40 cycles. The direct current fed to the cross winding 20 provides a pulsating current. The pulsating current comprises an alternating current superimposed on a direct current. As a result thereof, a D. C. flux is produced in the intersecting members to provide a saturating or biasing flux. A differential flux produced by the D. C. saturating flux and the alternating flux of cross winding I0 induces an alternating current signal in the secondary windings I5 and I6. The resonating circuit comprising condenser I4 and secondary windings l5 and I6 is tuned for 20 cycle signal.

Referring now to Fig. 3 which is a graphical illustration of the load regulation of the system shown in Fig. 2. The horizontal axis illustrates the output current in milliamperes at 20 cycles. The vertical axis illustrates the output volts at 20 cycles.

Referring now to Fig. 4 which is a schematic diagram showing how the present invention can be used, omitting the choke, electrolytic condenser and the additional secondary windings which were used for Fig. 2. The cross valve 28 herein used may again be of the type disclosed in the previously mentioned patents. The cross valve has two intersecting members. An air gap is shown in Fig. 4 at two points alternately opposite the horizontal intersecting member. Permanent magnet 30 is shown extending from the horizontal intersecting member to the top of the cross valve. Another permanent magnet 29 is shown extending from the other end of the horizontal intersecting member to the bottom of the cross valve 28. The primary winding 36 is wound through opposite diagonal corners of the intersecting members. serially connected to the primary winding 36 are two additional windings 31 and 38. Winding 38 is wound around one in tersecting member and winding 3! is wound around the other intersecting member. The power supply providing volts at 60 cycles energizes the primary winding 36 and the two I aeoarss is wound through the other diagonal corners of the intersection of the cross valve 28. The cross winding 35 is displaced 90 degrees from the primary winding 36. Condenser 3| is connected to the cross winding 35 to provide a resonant circuit. The output circuit comprises two secondary windings 33 and 34 and the condenser 32. The winding-33 is wound around the same intersecting member as in the additional wind-ing 31 but at an opposite point. The secondary winding 34 is wound around the same intersecting member as is additional winding 38 but at an opposite point. The output circuit comprising condenser32 and secondary windings 33 and 34 is tuned to the output frequencyat cycles. In more detail, a 130' volt 60 cycle power supply energizes the additional windings 31 and-38 and the primary winding 36. The permanent'magnets 36- and 29 produce a D. C. saturating flux in the core of the cross valve 28. The differential flux produced by the D. C. saturating flux and the alternating flux produced by the primary winding 36 induces a voltage in the resonating circuit comprising the cross coil and the condenser 3|. The circuit including cross coil 35 and the condenser 3| is tuned to 40 cycles. It is to be noted that there is no mutual inductance between the coil 35 and the coi1-36, until the magnetic core 28 has reached a point of near saturation which is produced by the D. C..magnetizing flux.

A voltage is now produced in the secondary windings 33 and 34 of the output circuit. The induced voltage is produced by a flux difierential caused by the D. C. saturating flux produced by the permanent magnets 30 and 29 and. the alternating flux produced by the winding 35. As a result thereof a 20 cycle voltage is induced in the windings 33 and 34, since a resonating circuit comprising these respective windings and the condenser 32 is tuned for that frequency. The 20 cycle frequency of the output winding plus the 40 cycle frequency of the cross winding equals the 60 cycle input frequency of the primary winding.

Referring now to Fig. 5, a cross valve 39 herein used may be of the type disclosed in the previously mentioned patents. The cross valve has two intersecting members forming two pair of diagonally opposite corners. A primary yvinding 44 is wound diagonally through two corners of the intersection. Serially connected to the primary winding 44 are two auxiliary windings 41 and 46. The power supply providing 130 volts at 60 cycles energizes the primary winding 44 and the auxiliary windings 46 and 41. In parallel with the auxiliary winding 41 is a rectifying circuit comprising inductance coil 48, condenser 56 and rectifier 53. In parallel with the auxiliary winding 46 is another rectifying circuit comprising inductance coil 49, condenser 5|, and rectifier 52. A cross winding is wound around the other diagonal corners of the intersection of the cross valve 39. Condenser 4| is connected to the cross winding to provide a resonating circuit. The output circuit comprises condenser 46 and secondary windings 42 and 43. Secondary winding 42 is wound around the same intersecting member as is auxiliary winding 46, but at an opposite end. Secondary winding 43 is wound around the same intersecting member as is auxiliary winding 41, but at an opposite end. The condenser 40 provides a resonating circuit with the secondary windings 42 and 43 to oscillate at 20 cycles. In more detail, the 130 volt cycle power supply energizes the primary winding 44 and the auxiliary windings 41 and 46 over the following path:

power supply, auxiliary winding 41, primary windings 44, auxiliary winding 46 and back to the power supply. A direct current is produced in the auxiliary winding 41 by the rectifying circuit over the following path: rectifier 53, auxiliary winding 41, inductance coil 48 and back to the rectifier 53. In a similar manner direct current is produced in the auxiliary Winding 46 over the following path: rectifier 52, inductance coil 5|, auxiliary winding 46 and back to the rectifier 52. The rectified current in the auxiliary coils 41 and 46 produces D. C. magnetizing fluxes which are opposing one another. As a result thereof, voltage is induced in the cross winding 45 by adifferential flux produced by the flux of the primary winding of the coil 44 and the D. C. saturating flux produced by the auxiliary windings 46 and 41. The circuit comprising the cross coil 45 and condenser 4| oscillates at 40 cycles.

A voltage is now induced in the secondary windings 42 and 43 which is caused by a differentialflux. This difierential fiux is produced by the D. C. saturating flux provided by the auxiliary windings 41 and 46 and alternating flux provided by the cross winding 45. The output circuit, comprising secondary windings 42 and 43 and condenser 40, oscillates at the tuned frequency 20 cycles.

Referring now to Fig. 6 which is a schematic diagram showing how a D. C. field can be produced using a low voltage rectifier on the leg coils. Cross valve 54 herein used may be of the type disclosed in said previously mentioned patents. The cross valve has two intersecting members forming two pairs of opposite diagonal corners. An input winding 69 is wound through a pair of the opposite diagonal corners at the intersection. Serially connected to the primary winding 66 are two auxiliary windings 63 and 6|. Auxiliary winding 63 is wound around one of the intersecting members, while winding BI is wound around the other intersecting member. saturating winding 64 is wound on the same intersecting member as is wound auxiliary winding 63. In a similar manner, the saturating winding 62 is wound around the same intersecting member as is wound the auxiliary winding 6|. Additional winding 1| is wound through the same diagonal corners as is wound the primary winding 60. The primary winding 60 and the additional winding 1| are magnetically coupled. A circuit comprising rectifier 66, 61, 68, 69 and condenser 65 connects the saturating windings 64 and 62 with the additional winding 1|. The cross winding 59 is wound through the other opposite diagonal corners of the intersection and is displaced degrees from the primary winding 66. A condenser 56 forms an oscillating circuit with the cross winding 59 to oscillate at 40 cycles. The output circuit comprises secondary windings 51 and 58 and the condenser 55 and is tuned to 20 cycles. The secondary winding 51 is wound around the same intersecting member as is auxiliary winding 6|, but at an opposite point. The secondary winding 58 is wound around the same intersecting member as is auxiliary winding 63, but at an opposite point. In more detail, the power supply providing volts at 60 cycles energizes the auxiliary windings 63 and 6| and the primary winding 68. The additional winding 1| is magnetically coupled to the primary winding 66 and thereby a voltage is induced in the additional winding 1|. As a result thereof, a rectified voltage is produced in the saturating windings 64 and 62 over the following path: additional winding H, rectifier 59, saturating winding 64, saturating winding 62, rectifier 67 and back to the additional winding H. The saturating windings 64 and 52 produce a D. C. saturating flux for the cross valve 54 thereby providing a biasing flux. Voltage is induced in the cross winding 59 by a differential flux produced by the D. C. saturating flux and an alternating flux. The D. C. saturating fiux which is a biasing flux is produced by the windings 64 and 62. The alternating current flux is produced by the windings 62, 63 and 60. Since the cross winding 59 is tuned to 40 cycles by the condenser 56, that circuit will oscillate at the desired frequency. As a result thereof, voltage is induced in the secondary windings 51 and 58 which is caused by a diiferential flux. The differential flux is produced by the D. C. magnetizing flux and the alternating current flow. The last mentioned D. C. saturating flux is provided by the saturating windings 64 and 62 and the alternating current flux is produced by the cross winding 59. Since the condenser 55 is tuned with the secondary windings 51 and 58, to oscillate at 20 cycles, the output frequency derived from this system is a 20 cycle signal.

Although I have described my invention with a certain degree of particularity it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the completion and arrangement of parts may be resorted to without departing from the true spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. In a static frequency changer, a saturable magnetic core having a pair of intersecting members, a primary winding wound through one pair of diagonally opposite corners of the intersection, a secondary winding wound around said pair of intersecting members, a source of alternating current connected to said primary winding for providing an input signal, a load circuit connected to said secondary winding, a single cross winding wound through the other pair of diagonally opposite corners of said intersection, rectifier means for producing a direct current, resonating means for producing an alternating current of a frequency different from said input signal frequency, said resonating means including said single cross winding, means inductively coupled to said primary winding for supplying a current to said rectifier means connected to said single cross winding for producing a biasing flux in said magnetic core, said alternating current in said cross winding inducing a differential flux in said magnetic core, whereby alternating currents having a frequency integrally related to the frequency of said source is delivered to saidload circuit.

2. In a static frequency changer, a saturable magnetic core having a pair of intersecting members, a primary winding wound through one pair of diagonally opposite corners of the intersection, a secondary winding wound around said pair of intersecting members, a source of alternating current connected to said primary winding for providing an input signal, a load. circuit connected to said secondary winding, a source of direct current, a single 'cross winding wound through the other pair of diagonally pposite corners of said intersection and continuously energized b said source of direct current for producing a biasing flux in said core, resonant circuit means including said cross winding inductively coupled to said source of alternating current for producing an alternating current in said cross winding in turn producing a differential flux in said core whereby alternating currents having a frequency integrally related to the frequency of said source of alternatin current are delivered to said load circuit.

3. In a frequency changer, a magnetic core structure having two intersecting members, a primary circuit including a coil wound through a pair of diagonal corners of the intersection to provide the input signal, a secondary circuit including a condenser and a coil wound around the two intersecting members and tuned to the desired output signal, a source of current, said current connected to said primary circuit, a differential circuit including only one coil wound through the other pair of diagonal corners of the intersection, means connected to said source of current and said differential circuit for providing a continuous pulsating current in said difierential circuit, said current in said coil in said difierential circuit thereby inducing a continuous pulsating flux in said core whereby said pulsating current provides a flux for self-starting characteristics so that said secondary circuit oscillates at the tuned frequency in response to said fiux in said magnetic core structure.

4. In a frequency changer, a magnetic core structure having two intersecting members, a

primary circuit including a coil wound through a pair of diagonal corner of the intersection, a first source of current connected across said primary circuit for energizing said primary circuit to provide the input signal, a secondary circuit including a condenser and a coil wound around the two intersecting members and tuned to a desired output signal, a source of pulsating direct current, a resonant circuit connected thereto, a single cross winding wound through the other pair of diagonal corners of the intersection and forming part of said resonant circuit for providing continuous pulsating current, whereby said cross winding provides a biasing flux and a differential flux for said magnetic core structure so that said secondary circuit oscillates at the tuned frequency in response to said flux differential in said magnetic core structure, thereby pro viding self-starting characteristics.

5. In a frequency changer, a magnetic core structure having two intersecting members, a primary circuit including a coil wound through a pair of diagonal corners of the intersection to provide the input signal, a secondary circuit including a condenser and a coil wound around the two intersecting members and tuned to the desired output signal, an additional circuit including a coil wound through said pair of diagonal corners of the intersection and inductively coupled to said primary circuit for providing continuous oscillations, a differential winding having a condenser connected in parallel therewith wound through the other pair of diagonal corners of the intersection, rectifier means connected to said additional circuit for rectifying part of the input signal induced in said additional circuit, said differential winding connected to said additional winding for providing a continuous current in said differential winding in response to the continuous oscillations of said additional winding and said rectifier means for providing a biasing flux in said magnetic core structure, and means comprising said differential winding operated responsive to the input signal flux and the biasing flux for producing a differential flux in said core, whereby said secondary circuit oscillates at the tuned frequency in response to said flux differential and said biasing flux in said magnetic core structure, thereby providing selfstarting characteristics.

6. In a frequency changer, a magnetic core structure having two intersecting members, a primary circuit including a coil wound through a pair of diagonal corners of the intersection to provide the input signal, a secondary circuit including a condenser and a coil wound around the two intersecting members and tuned to a desired output signal, an additional circuit including a coil wound through said pair of diagonal corners of the intersection inductively coupled to said primary circuit to provide continuous oscillations, a differential circuit including a condenser and a coil wound through the other pair of diagonal corners of the intersection. and a rectifier interconnecting said additional circuit and said differential circuit for rectifying part of said input signal induced in said additonal circuit to provide a continuous current in said differential circuit in response to the continuous oscillations of said additional circuit for providing a biasing flux in said magnetic core structure, and means includin said differential circuit operated responsive to the input signal flux and the biasing flux for producing a differential flux in said core, whereby said secondary circuit oscillate at the tuned frequency in response to said biasing flux and said differential flux to provide self-starting characteristics.

7. In a frequency changer as claimed in claim 6, and including an electrolytic condenser connected in parallel to said differential circuit and charged by the rectified current for improving the load regulation.

8. In a frequency changer, a magnetic core structure having two intersecting members, a

source of alternating current, a primary circuit including a coil wound through a pair of diagonal corners of the intersection connected across said source of alternating current to provide the input signal in response to energization by said source of current, a secondary circuit including a condenser and a coil wound around the two intersecting members and tuned to a desired output signal, a source of direct current, a resonant circuit comprising a coil and a condenser tuned to a frequency which is the difference between said input signal frequency and said output signal frequency connected thereto, said last mentioned coil wound through the other pair of diagonal corners of the intersection, said resonant circuit operating responsive to said direct current and said input signal for providing continuous pulsating current whereby said last mentioned coil provides a biasing flux and a differential flux for said magnetic cross structure so that said secondary circuit oscillates at the tuned frequency in response to said flux differential in said magnetic core structure, thereby providing self-starting characteristics.

9. In a frequency changer, a magnetic core structure having two intersecting members, a primary circuit including a coil wound through a pair of diagonal corners of the intersection, a source of alternating current connected to said primary circuit to energize said primary circuit for providing the input signal whereby an input flux is induced in said core, a secondary circuit includin a condenser and a coil wound around the two intersecting members and tuned to the desired output signal, an additional winding wound around said pair of diagonal corners and inductively coupled to said primary circuit to provide continuous oscillations in said additional winding, a differential circuit including a condenser and a coil wound through the other pair of diagonal corners of the intersection, said last mentioned coil and condenser resonant to a frequency other than the input frequency, a bridge rectifier having two pairs of diagonal corners, one pair of diagonal corners of said rectifier connected to said additional circuit and the other pair of diagonal corners of said rectifier connected to said difierential circuit whereby said difierential circuit provides a continuous pulsating current in response to the rectification of said continuous oscillating current in said additional winding by said bridge rectifier and said input flux whereby said differential circuit provides a flux in said magnetic core structure so that said secondary circuit oscillates at the tuned frequency in response to flux in said magnetic core structure, thereby providing self-starting characteristics.

10. A frequency changer as claimed in claim 9,

' and including an electrolytic condenser connected to said other pair of diagonal corners of said rectifier, whereby said rectified current charges said electrolytic condenser to provide improved load regulation.

11. In a frequency changer, a saturable magnetic core having a pair of intersecting members, a primary winding wound through one pair of diagonally opposite corners of the intersection, a secondary winding wound around said pair of intersecting members, a resonant circuit resonant at a certain frequency and including said secondary winding, a source of alternating current connected to said primary winding for providing an input signal, the frequency of said source of alternating current being greater than the frequency of said resonant circuit, a load circuit connected to said secondary winding for providing an output signal, a single cross winding wound through the other pair of diagonally opposite corners of said intersection, a condenser connected across said single cross'winding forming a circuit resonant at a frequency which is the difference between the aforementioned frequencies, and means comprising a direct current source connected across said single cross winding for producing a biasing flux in said magnetic core, and means comprising said last mentioned means, said source of alternatin current, and said circuit including said cross winding and condenser for producing a differential flux in said. magnetic core, whereby alternating currents having a frequency integrally related to the frequency of said source are delivered to said load circuit.

HAROLD J. MCCREARY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,862,211 Dowling June 7, 1932 2,324,634 McCreary July 20, 1943 2,445,857 McCreary July 27, 1948 2,455,078 McCreary Nov. 30, 1948 2,461,992 McCreary Feb. 15, 1949 2,468,878 Huge May 3, 1949 

